Java 5 (JDK 1.5) will be supported in the J2EE edition of BlueDragon (BD/J2EE), as of the 6.2.1 release, but the Server and JX editions (for Windows and Linux) will continue to bundle JDK 1.4.2, and that's the only version of the JDK we'll support for those editions (it's always been the case that we only support the bundled JDK for Server and JX on Windows/Linux).
BD Server and JX for Mac OS X support the version of the JDK bundled with Mac OS X. This could be either JDK 1.4 or 1.5 depending on the version of Mac OS X.